A polarized capacitor has positive and negative terminals. In the design and fabrication of an electronic circuit, it is important to correctly orient each polarized capacitor. The result of misorienting a polarized capacitor can be damaging to the circuit and dangerous to individuals. First, the circuit failure due to the misoriented capacitor can be latent and unpredictable. Second, the resultant failure of the capacitor may be sudden and violent, causing physical damage to surrounding equipment and injury to personnel.
Heretofore, reliable determination of the orientation of a polarized capacitor by automatic means after connection of the capacitor into a circuit has been problematic. In general, no measurable parameter of the capacitor reliably indicates its orientation. While some polarized capacitors exhibit greater leakage current prior to failure when reverse-biased than when forward-biased, this phenomenon is not true of all polarized capacitors and is therefore not a reliable indicator of orientation. Also, for most circuits, only a limited amount of bias potential may be applied to a capacitor without having the measurement degraded by the effect of surrounding components in the circuit. Therefore, methods based on the leakage current are not universally applicable or reliable when performed in-circuit.
Currently, correct orientation of the capacitors can be ensured only by visual inspection, which is costly and error-prone. If circuit boards are not inspected, the danger of board failure or destruction exists.
Therefore, a need has arisen in the industry for a method and apparatus for in-circuit determination of the orientation of a polarized capacitor.